Hydrogen peroxide is an environmentally clean and versatile oxidizing agent used extensively in paper and pulp industries as a bleaching agent, for water purification and disinfection, for wastewater treatments and also in the preparation of fine/bulk chemicals by various oxidation processes. Currently most widely practiced commercial scale production of hydrogen peroxide is based on an auto oxidation process employing alkyl anthraquinone as the working material. This process involves reduction of alkyl anthraquinone dissolved in an organic working solution to alkyl anthraquinol. The alkyl anthraquinol is oxidized by air to produce hydrogen peroxide and alkyl anthraquinone, which is recycled in this process. This process comprises a number of operations involving reduction, oxidation, separation by aqueous extractions, refining and concentration, making the process complex. Apart from the requirements of high capital and operation costs, this process has following limitations and disadvantages:
Non-selective in hydrogenation, hence loss of anthraquinone.
Difficulties in separation hydrogenation catalyst and degradation products.
Need for the regenaration of used hydrogenation catalyst.
Need for the removal of organic matters from the extracted H2O2 solution.
Waste treatment and disposal of undesired side products of the cyclic process.
Demand for hydrogen peroxide has been increasing day-by-day for oxidizing organic compounds to value added products, waste-water treatment and water disinfection. Hence, there is a great practical need for replacing the anthraquinone process by an environmentally clean and more economic process. A number of processes based on the direct oxidation of hydrogen-to-hydrogen peroxide, using a solid catalyst comprising palladium, were disclosed in several patents, for example U.S. Pat. Nos. 4,681,751; 4,772,458; 4,832,938; 4,889,705; 5,135,731; 5,169,618; 5,399,334; 6,534,440; EP 504,741, A1; WO 9412428 A1; EP 621,235 A1; GE 4,172,918; JP 01133909 A2; EP 366419 A1; WO 9314025 A1. However, the direct oxidation of hydrogen-to-hydrogen peroxide is a highly hazardous process and hence inspite of the extensive invention, this process is not yet commercialized. Apart from its hazardous nature, the direct hydrogen-to-hydrogen peroxide oxidation processes have other limitations such as lower selectivity in the formation of hydrogen peroxide, use of highly corrosive liquid medium for the reaction and low concentration of hydrogen peroxide produced in the process.
Because of the limitations of the prior art processes for the production of hydrogen peroxide, there is a great practical need for developing a novel environ-friendly process for the production of hydrogen peroxide. The present invention was made for this purpose.